Complete experimental investigation on the instantaneous strain hardening behaviour of powder metallurgy （P/M） preforms of pure iron, Fe 0.35%C, Fe-0.75%C and Fe-1.1%C was carried out. The strain hardening be haviou...Complete experimental investigation on the instantaneous strain hardening behaviour of powder metallurgy （P/M） preforms of pure iron, Fe 0.35%C, Fe-0.75%C and Fe-1.1%C was carried out. The strain hardening be haviour of the above-mentioned P/M sintered steel preforms with aspect ratio of 0.4 under triaxial stress state condition was determined by cold upsetting under nil/no and graphite lubricant conditions. The instantaneous strain hardening value （ni）, strength coefficient （Ki）, and the stress as a function of strain and densification were obtained and analyzed. Furthermore, a relation was obtained from a semi-log plot of stress against relative density and analyzed to study the hardening behaviour owing to densification as stress was a function of induced strain as well as densification in the P/M materials.展开更多
An experimental investigation on the workability behaviour of sintered Fe-0.35C steel preforms under cold upsetting,have been studied in order to understand the influence of aspect ratio and lubrication condition on t...An experimental investigation on the workability behaviour of sintered Fe-0.35C steel preforms under cold upsetting,have been studied in order to understand the influence of aspect ratio and lubrication condition on the workability process.The above mentioned powder metallurgy sintered preform with constant initial theoretical density of 84% of different aspect ratios,namely,0.4 and 0.6 respectively were prepared using a suitable die-set assembly on a 1 MN capacity hydraulic press and sintered for 90 min at 1200 ℃.Each sintered preform was cold upset under nil/no and graphite frictional constraint,respectively.Under the condition of triaxial stress densification state,axial stress,hoop stress,hydrostatic stress,effective stress and formability stress index against axial strain relationship was established and presented in this work.Further more,attained density was considered to establish formability stress index and various stress ratio parameters behaviour.展开更多
A systematic method to construct the workability diagram for powder metallurgy （P/M） materials has been proposed. Preforms of Fe-0.8 %C, Fe-0.8% C-1% Mo and Fe-0.8 % C 2 % Mo were prepared to the relative den-sity o...A systematic method to construct the workability diagram for powder metallurgy （P/M） materials has been proposed. Preforms of Fe-0.8 %C, Fe-0.8% C-1% Mo and Fe-0.8 % C 2 % Mo were prepared to the relative den-sity of 0.86 with two different geometries through primary operations of P/M processes. Each sintered preform was cold upset forged with incremental compressive loading of 0.04 MN under three different lubricant conditions till a visible crack appeared at the free surface. Oyane＇s fracture criterion was used to develop a theory to study P/M prod-ucts. The least square method was used to determine the constants in fracture criteria and these equations were even- tually used to construct workability diagram. It is found that the proposed method was well in agreement with the experimental results.展开更多
文摘Complete experimental investigation on the instantaneous strain hardening behaviour of powder metallurgy （P/M） preforms of pure iron, Fe 0.35%C, Fe-0.75%C and Fe-1.1%C was carried out. The strain hardening be haviour of the above-mentioned P/M sintered steel preforms with aspect ratio of 0.4 under triaxial stress state condition was determined by cold upsetting under nil/no and graphite lubricant conditions. The instantaneous strain hardening value （ni）, strength coefficient （Ki）, and the stress as a function of strain and densification were obtained and analyzed. Furthermore, a relation was obtained from a semi-log plot of stress against relative density and analyzed to study the hardening behaviour owing to densification as stress was a function of induced strain as well as densification in the P/M materials.
文摘An experimental investigation on the workability behaviour of sintered Fe-0.35C steel preforms under cold upsetting,have been studied in order to understand the influence of aspect ratio and lubrication condition on the workability process.The above mentioned powder metallurgy sintered preform with constant initial theoretical density of 84% of different aspect ratios,namely,0.4 and 0.6 respectively were prepared using a suitable die-set assembly on a 1 MN capacity hydraulic press and sintered for 90 min at 1200 ℃.Each sintered preform was cold upset under nil/no and graphite frictional constraint,respectively.Under the condition of triaxial stress densification state,axial stress,hoop stress,hydrostatic stress,effective stress and formability stress index against axial strain relationship was established and presented in this work.Further more,attained density was considered to establish formability stress index and various stress ratio parameters behaviour.
文摘A systematic method to construct the workability diagram for powder metallurgy （P/M） materials has been proposed. Preforms of Fe-0.8 %C, Fe-0.8% C-1% Mo and Fe-0.8 % C 2 % Mo were prepared to the relative den-sity of 0.86 with two different geometries through primary operations of P/M processes. Each sintered preform was cold upset forged with incremental compressive loading of 0.04 MN under three different lubricant conditions till a visible crack appeared at the free surface. Oyane＇s fracture criterion was used to develop a theory to study P/M prod-ucts. The least square method was used to determine the constants in fracture criteria and these equations were even- tually used to construct workability diagram. It is found that the proposed method was well in agreement with the experimental results.
